Traditional downlights have two spring fixing structures on two sides. Each spring fixing structure is axially pressed and placed in an inverse T slot. This technique has been applied in the industry for many years. The existing problem is that the installation of the spring fixing structure is complex and can only be processed by human hands, which leads to low productivity. On the other hand, an end of the spring fixing structure can get loose and slide out of the inverse T slot during an installation process because of unbalanced forces. Thus, it is in great need as to how to design a new downlight fixing structure that can have the fixing function of a spring and also can be installed by automatic machine.